1. Field of the Invention
The present invention relates to a multiple annular combustor for a gas turbine engine and, more particularly, to a dome assembly for a multiple annular combustor where heat shields are mechanically attached to the dome plate.
2. Description of Related Art
It is well known in the art for multiple annular combustors of gas turbine engines to employ heat shields to protect the dome plate from excessive heat. Such heat shields preferably include annular centerbodies extending axially therefrom in order to separate the domes or stages of the combustor. By doing so, combustion stability of the pilot stage is ensured at various operating points and primary dilution air is allowed to be directed into the pilot stage reaction zone.
One particular heat shield and centerbody design utilized with a triple annular combustor is disclosed in U.S. Pat. No. 5,323,604, which is also owned by the assignee of the present invention. As seen therein, the heat shield/centerbody is brazed to the dome structure. While brazing of heat shields and centerbodies to the dome structure of a combustor is commonly employed in the art, it has been found that debrazing and rebrazing a damaged heat shield/centerbody is difficult during repair and requires engine teardown.
Additionally, it will be seen in U.S. Pat. No. 5,323,604 that ferrules are positioned between the forward side of the dome and certain retainer pieces, where the ferrules are able to float radially and circumferentially so as not to load up the fuel nozzle assembly. Accordingly, the fuel nozzle contains a piston ring seal for sealing of the ferrule to the fuel nozzle, while the centerbodies include "C" seals on the outer extremes thereof to prevent leakage as they are cooled. Therefore, a large number of components are utilized and must be assembled, which can become extremely difficult.
Further, it will be understood that the centerbodies in U.S. Pat. No. 5,323,604 must be preloaded to compress the "C" seal and tack welded in place, whereupon they are brazed for final attachment along with the retainers for the ferrules. It has been found that inspection of this assembly for full joint penetration is impossible, therefore bringing the total joint integrity into question.
In light of the foregoing, it would be desirable to have a heat shield and centerbody assembly which can be attached to a dome structure of a multiple annular combustor that does not have the associated problems of brazing, and yet still provides the sealing required to prevent air from entering the combustion zone.